1. Field of the Invention
This invention relates to an improved rotary cutting tool, and more particularly, to a method and apparatus for drilling a hole in a working surface utilizing a reamer bit in combination with a drill bit.
2. Description of the Related Art
In the fields of industrial, mining and construction tools, drill bits having complex cutting element arrangements and cutting tool inserts are commonly used. In rock drilling operations, it is the conventionally known practice to drill holes in a rock formation by a rotary drill assembly or by a rotary percussion drill assembly. These assemblies include a drill pot that carries a hydraulic motor having a motor shaft rotatably connected to a bevel gear which meshes with another bevel gear rotatably journaled on a support member or hub within the drill housing. It is affixed to a rotatable head or cover, which has a seat into which the shank of a drill steel is received. A drill bit is positioned on the upper end of the drill steel. With this arrangement, rotation of the motor shaft is transmitted to the drill steel to rotate the drill bit.
Many examples of drill bits are known in the art. U.S. Design Pat. No. 178,899 discloses an ornamental design for a drill bit. The drill bit includes three teeth that extend from the distal end of the drill bit and intersect at a point in the center of the distal end. The teeth are separated by a large angular space. The cutting surface of each tooth includes a series of uniform steps.
U.S. Pat. No. 5,184,689 discloses a rotary drill bit that includes a cylindrical body, two dust openings, and a working surface having an insert. The insert includes a simple tapered edge. The drill bit also includes a back relief surface, which can help to remove dislodged material from a working surface, as the drill bit rotates during drilling operations.
U.S. Pat. No. 5,433,281 discloses a roof drill bit having a plurality of equally spaced cutting elements. The cutting elements are V-shaped, not rounded. The cutting elements are spaced symmetrically about an axis that runs from the connecting end of the drill bit to the distal end of the drill bit.
U.S. Pat. No. 4,771,834 discloses a drill bit that includes a plurality of cutting teeth extending from a cutting surface on the distal end of a drill bit. The cutting teeth also extend radially, outwardly from the center of the cutting surface and intersect at the center point of a cutting surface on the drill bit. Each tooth includes a pair of conical cutting elements symmetrically positioned on the tooth. The bit also includes a plurality of pockets for collecting debris from a working surface.
U.S. Pat. No. 4,471,845 discloses a drill bit that includes a plurality of cutting teeth extending from a cutting surface on the distal end of a drill bit. The cutting teeth also extend radially, outwardly from the center of the cutting surface and intersect at the center point of the cutting surface on the drill bit. Each tooth includes a plurality of rounded cutting elements symmetrically positioned on the tooth.
U.S. Pat. No. 6,290,007 discloses a drill bit that includes a plurality of cutting teeth extending from a cutting surface on the distal end of a drill bit. The cutting teeth also extend radially, outwardly from the center of the cutting surface. Each tooth includes a plurality of cutting elements symmetrically positioned on the tooth. Accordingly, conventional drill bits include symmetrically positioned cutting elements and cutting teeth.
Polycrystalline diamond (PCD) is now in wide use, sometimes called polycrystalline diamond compacts (PDC), in making drill bits. U.S. Pat. No. 6,427,782 discloses that PCD materials that are formed of fine diamond powder sintered by intercrystalline bonding under high temperature/high pressure diamond synthesis technology into predetermined layers or shapes; and such PCD layers are usually permanently bonded to a substrate of “precemented” tungsten carbide to form such PDC insert or compact.
The term “high density ceramic” (HDC) is sometimes used to refer to a mining tool having a PCD insert. “Chemical vapor deposition” (CVD) and “Thermally Stable Product” (TSP) diamond-forms may be used for denser inserts and other super abrasive hard surfacing and layering materials, such as layered “nitride” compositions of titanium (TiN) and carbon (C2 N2) and all such “hard surface” materials well as titanium carbide and other more conventional bit materials are applicable to the present invention.
Although many of the drill bits solve the problems discussed above, there is a need for an unconventional reamer bit that has the ability to work in combination with an unconventional “hard surface” drill bit to drill larger holes.